Activities such as golf or tennis require a player to swing an apparatus (e.g. a club or racquet) along a swing path to strike an object with a strike face. The swinging apparatus propels the object in a direction perpendicular to the strike face at the point of impact. If the strike face is square to the swing path, the object will travel along the swing path which is the intended direction of travel. However, if the strike face is angled away from (and not square to) the swing path, the object will travel along a path deviating away from the swing path.
A player's control of the apparatus during a swing (e.g. its swing velocity and its orientation relative to the swing path) depends on the player's, control of many factors, including complex biomechanical interactions between the player and the apparatus. The player's control of these factors directly affects the object's direction of travel. Since it can be difficult for a player to be always in conscious control of the factors affecting the swing, it is difficult to ensure that the strike face is always square to the ball in each swing. Accordingly, there will always be some degree of variation in the object's direction of travel relative to the swing path between different swings. In the absence of suitable feedback, it is difficult for players to identify alignment errors and make corrections when the strike face is not square to the swing path during a swing.
Several solutions have been proposed. U.S. Pat. No. 7,427,238 describes a golf swing guide device. The device has a housing that is releasably attachable to a lower end of a golf club shaft. The housing includes a laterally extending stationary member pointing in a fixed direction perpendicular to the club face (representing the ball's intended direction of travel). The housing also includes a wind vane extending away from the stationary member, and which is pivotable about an axis parallel to the shaft of the club. The wind vane responds to air movement to align itself along the swing path of the club. A magnet is attached to the wind vane, the position of which (relative to the housing) is electronically detected based on the relative proximity of the magnet to two separate Hall effect sensors, each being fixed to a different respective portion of the housing. When the strike face is not square with the ball at the point of impact, the electronic circuit of the device generates (at the point of impact) an audible or viewable signal representing the strike face's deviation from the swing path based on the wind vane's direction and angular deviation relative to the stationary member.
There are several problems with this approach. The device is unable to produce feedback in the absence of electrical power. Also, the device only produces a signal at the moment of impact between the club face and the ball, and does not attempt to provide the player with continuous feedback during the entire swing. The device therefore does not give players the opportunity to correct a swing before striking the ball. The device is also unable to provide feedback on club velocity, which is an important factor contributing to a player's control of the swing. The device also relies on electrical power (from a battery) in order to be able to detect the angular deviation the wind vane and generate the feedback signal.
A further problem with this approach is that the use of a wind vane alone can often cause the housing to travel in an unstable manner. In order for the wind vane to operate efficiently, and align itself with the swing path, it requires a stable wind flow for stability. However, during a swing of a golf club, the wind flow will quite often be turbulent and unstable, due partly to the high velocity at which the golf club travels, and also due to side winds. As a result of this turbulent and unstable wind flow, the housing may tend to ‘flutter’, and not smoothly align itself to the swing path.
Other proposed solutions are described below, which involve detecting misalignment between the club face and the ball (or swing path) based on inertia, or the direction or speed of air flow relative to the apparatus. None of these solutions involve detecting the position of a member that pivots relative to the apparatus in response to air flow.
For example, U.S. Pat. No. 5,836,829 describes both a mechanical and electronic embodiment of a golf swing training device. The mechanical embodiment comprises an arm that extends in parallel to the club face of a golf club, and is attached to the shaft of the club. The arm has a lever (with a weight attached at one end) that pivots about a horizontal hinge. An outer end of the lever (distal from the shaft) has a pendulum (incorporating a pin) that pivots about a vertical hinge. In normal operation, the club face and the pendulum are aligned perpendicularly to the swing path producing a straight drive. This aligns the pin to a hole in the arm. The forces acting on the weight during a swing causes the lever to move towards the club head, and compress a diaphragm producing a “popping” sound. If the club face is oriented to produce a slice or a hook, the pendulum moves the pin away from the hole so that the lever is unable to move towards the club head and compress the diaphragm (so no “popping” sound is produced). The electronic embodiment includes accelerometers and light sensors for detecting any offset of the pendulum relative to a position perpendicular to the swing path. The device electronically detects and generates four distinct sounds to provide the player with instantaneous feedback on the smoothness throughout the swing and the club face orientation relative to the ball at the point of impact. A sound is produced when the player's swing is correctly aligned. If a slice or hook would have occurred, due to improper club head orientation, the device produces a sound of rising or falling pitch. A sound is produced if there is excessive acceleration during the backswing to indicate an unsmooth swing.
U.S. Pat. No. 3,776,556 describes a golf swing training device attached to a golf club shaft. The device has a “tear drop shaped” hollow body defining two separate channels respectively in the upper and lower half of the body. Each channel includes a different whistle (e.g. for producing a different sound). The channels constitute two wind chambers angled so as not to trap air when the club travels straight ahead perpendicularly to the intended line of flight. But when the club is being drawn diagonally across the ball (e.g. inwardly as in FIG. 4B or outwardly as in FIG. 4C), air passes through the wind chamber on the frontally exposed side and the respective whistle instantly indicates whether a hook or slice swing has resulted.
U.S. Pat. No. 3,730,530 describes a golf swing training device comprising a whistle and a fixing member. The fixing member includes a suction disk and a portion adapted to hold the whistle. The whistle includes a changeable vibration plate, a plate receiving tray and a cylindrical body for retaining the plate and the tray. The suction disk attaches the device to the head of a golf club. When attached, the whistle is ideally square in relation to the club face. When the club is swung at an appropriate speed and angle (relative to the air inlet of the device), the whistle captures air to produce a sound.
U.S. Pat. No. 4,789,160 describes a swing position indicator device for a sports implement (e.g. a golf club). The device is attached to the shaft of a sports implement, and includes two position orientation sensors. The sensors detect the pitch and roll of the striking surface respectively. When both of these sensors indicate that the striking surface is properly oriented, a sound is generated. The sound is maintained for as long as the striking surface is properly oriented.
U.S. Pat. No. 5,277,428 describes a golf club swing training device. The device includes a housing for mounting onto a golf club in at least two different positions. When mounted in a first position, a transducer inside the housing monitors deviation of golf club travel from a linear direction during a swing. When mounted in a second position, the transducer monitors the acceleration of the golf club during a swing. The transducer comprises of optical reflective detectors for monitoring the offset positions of a mass on the upper end of a cantilevered spring having its lower end fixed to a circuit board including an aperture therein in which the mass is disposed.
It is therefore desired to address one or more of the above problems, or to at least provide a useful alternative.